i. Geography

The city of Bactra, later Balḵ, owed its importance to its position at the crossing of major routes: the west-east route along the foot of the Khorasan and Hindu Kush mountains from Iran to Central Asia and China, and the route by left bank tributaries of the Oxus and passes through the mountains of central Afghanistan to northwestern India. The river of Balḵ (Balḵāb) gives easy access by the valley of its tributary the Dara-ye Ṣūf and the Qarā Kotal pass to the Bāmīān basin and thence to Kabul. This route has the advantage of being the westernmost of the roads over the Hindu Kush and thus the shortest for travelers from the west, as well as one of the easiest. Its existence must have been the main reason why a great city arose in the area where the Balḵāb debouches into the plain.

Within this area and on the irrigated alluvial fan, at a distance of about 12 km from the mountains, the city was built on a site (the Bālā Ḥeṣār of today) which was probably coextensive with a slight rise in the plain and perhaps adjacent to an old arm of the river. This is only a supposition, because adequate archeological exploration has not yet been carried out. In any case, the site subsequently grew higher through the gradual accumulation of the debris left by successive human occupants.